Automatic telephone system



Aug. 3, 1926. 1,594,610

' J. E. GARDNER AUTOMATIC TELEPHONE SYSTEM Filed Nov. 6, 1922 3 Sheets-Sheet 1 /9 y if Aug.' 3 1926; 1,594,610

J. E. GARDNER AUTOMATIC TELEPHONE SYSTEM Filed Nov. 6, 1922 3 Sheets- Sheet 2 Aug. 3,1926. 1,594,610

J. E. GARDNER AUTOMATIC TELEPHONE SYSTEM Filed Nov. 6, 1

JuZm EEarcfnEr Patented Aug. 3, 1926.

warren strains.

rarsnr orFicE.

JOHN E. GARDNER, OF CHICAGO, ILLINOIS, ASEEGNOR, BY MESIIE ASSIGNIHENTS, T0

AUTOMATIC ELECTRIC INC; 015' GHICAGOQILLINOIS, A CORPORATION OF DELA- HARE.

AUTOMATIC TELEPHONE SYSTEM.

The present invention relates in general to automatic telephone systems, but is more particularly concerned with small automatic systen'is that are used in mamrtacturing plants. mercantile establishments and the like. Systems of this character have become widely known as private automatic exchange systems. In order to meet the more exacting requirements oi the subscribers in these small systems it is the usual practice to .provide special features which are not supplied in larger automatic systems. f

One of these .lfeatures is lmown as code calling. This is an arrangement whereby, 1f the party called isnot at his telephone, a

code call may be sent through the establishment having the private autoi naticexchange by calling a special number. The desired partys code is sent'out to a number of bells or to signalling devices located at various points in the building. The called party responds to his call by dialing a special code answering number. I

It is with this codc callinp; arrangement that the present invention is concerned. The general object of the intention is to provide an improved type of code calling service.

arranged so ,thatwhcn a call is made to a party in the private automatic exchange that is entitled code call service. it the desired party does not respond within a certain length or time, his code call is automatically sent throughoutthe establishn'ient without the calling party having; to perform any operatioi'i. The called party responds in the .usual manner by dialin the code call an swering number.

Another object of the invention is to provide means for utilizing the code calling equipment, above mentioned for transmittine; 5 characteristic code signals in ordert-o enable the calling; subscribers to get in communication with -..=tain parties not equipped ith telephones. y

Refelringnowto the drawings, comprising Figs. 1, 2 and 3, su'iiicient apparatus showing; the inveution applied to a private automatic exchange is illustrated, by means of the usual circuit diagrams, to enable the invention to be readily described au'dunclcrstood.

Referring now particularly to Figl. in the upper left hand corner oi the drawing there is shown an automatic substation The substation A is of the ordinary awomatic type being provided with a ca vice S in addition to the usual talkin strumcaitalities. The line conductors l1 and 12 of the substation A terminate at the exchange in th line or trunk selecting switch C. I

.The line switch C is of the usual rotary type whose wipers move in a forward direction only. The linenswitc'h (3', together with a number of other line switches, has ac- 1 cess to trunk lines extending to connector switches, one of these belng the trunk llne leading to the connector H from the bank to avoid complicating the drawing this has. not been shown.

'Th substation A is similar to the sub station A already described. The line of th substation A terminates at the exchange in the line switch C as well as in multiple switches such as H. K

The line switch C is similar to the line switch C except that it is provided with a resistance in shunt of the switching relay.

This resistance is provided in order to give the subscriber at substation A the special service hereinbefore mentioned.

Relays, when shown with one end of their cores in solid black,are of the type which .are both slow to operate and slow to release.

Relays which are shown with one end of their. cores cross-hatched are of the type which are relatively quick to pull ;up, but are slow torelease.

Associated with the connector H and all the connectors .ot the exchange is a slow acting solenoid mechanism shown at S.

Thissolenoid controls certain circuitswhich bank contacts accessible to. the connector will be described in detailed explanation which is to follow. i

In Fig. 2 there is shown a finder switch D, which has access to all the subscribers lines that are entitled to the special service hereinafter mentioned.

In Fig. 8 there is shown the code calling equipment proper. This equipment comprises a code selecting switch F, which is of the vertical and rotary type, and an interrupter switch I, which is of the same mechanical construction as the ordinary rotary line switch.

' In order to completely describe the invention, the manner in which a call is made from one subscriber in the private automatic exchange to another subscriber therein will be described first.

For this purpose it will be assumed that the subscriber at substation A desires to communicate with the subscriber at substation A. To call this subscriber the party at substation A will remove his receiver and operate his calling device for the two-digits of the desired partys number.

When the receiver is removed at substation A a circuit is completed for the line relay 15 of the line switch C over the line conductors 11 and 12 in series. The line relay 15, upon operating, initiates the trunk selectingoperation of this switch in the usual manner. hen an idle trunk is selected, 'which, it will be'assumed, is the trunk line terminating in bank contacts 30-32, inclusive, the switching relay 141 is energized. Upon operating, relay 14, at its armature v18'places ground upon the test contact 31 of the seized trunk line in order to busy it. Additional results of the energization of relay 14 are that at armatures 17 and 19 the line conductors 11 and 12 are disconnected from the winding of the line relay 15 and from ground, respectively, and are extended by way of the front contacts of these armatures, wipers 27 and 29, bank contacts 30 and 32, through the upper and lower windings of the line rel-ay 51 of the connector H to battery and ground, respectively.

The line relay 51 of the connector H is energized over the calling line loop. Upon operating, relay 51, at its armature 63 closes a circuit for the slow acting relay 52. The latter relay, upon energizing, prepares the switch circuits for operation at arm-atures 66 and 65, and at armature 6 1 places ground upon the-release trunk conductor 49, thereby establishing a holding circuit for the switching relay 14 of the line switch C. This circuit may be traced as follows: from grounded release trunk conductor 49 by way of bankcontact 31, wiper 28,armature 18 and its front contact, through the winding of the switching relay 14;, and through the winding of the motor magnet 16 to battery.

It will be understood'that this holdingcircuit is established before the slow acting line relay 15 has had time to deenergize. A branch of this holding circuit may also be traced by way of the private normal conductor 20 to multiply connected bank contacts in the local connector switches such as H, whereby the said line is protected from intrusion during the connection.

The calling subscriber at substation A may now dial the first digit of the desired number. As a result of this operation, a series of interruptions is produced in the line circuit of the relay 51 and this relay deenergizes a plurality of times in response thereto. Ateach retraction of the armature 63 on the line relay, an impulse of current is sent to the vertical magnet 60. The circuit over which the first of these impulses is sent may be traced from ground by way of armature 63 and its back contact, armature 66 and its front contact, off normal springs 67 and 69, through the winding of the slow acting relay 53, and through the winding of the vertical magnet 60 to battery. As mentioned before, the above is the, circuit over which the first vertical magnet impulse is sent. However, upon the first vertical step of the switch, the ofi normal springs are shifted and the remaining impulses to the vertical magnet traverse a new circuit, which is similar to the one above described, except that it includes the off normal springs 67 and 68 and armature 70 on the slow acting relay 53, which is now energized. Magnet 60 operates to raise the switchwipers 95-98, inclusive, step by step until the said wipers are raised to the proper level of bank contacts in accordance with they number of interruptions in the digit dialed. The vertical wiper. 99 is also raised by the switch shaft to the proper level of bank contacts. This wiper is adapted to engage the vertical bank contacts such as 130 and to remain in engagement with them even when the switch shaft is rotated. This may be accomplished in any desired manner such as mounting wiper 99 on the switch shaft so that it is carried upward by the shaft but is free to permit the shaft to rotate. The slow acting relay 53 is energized in series with the vertical magnet 60 and maintains its armature attracted throughout the vertical movement of the switch thereby preserving the c0ntinuity of the vertical magnet circuit when the off normal springs are shifted. Shortly after the termination of the vertical movement the slow actingrelay 53 deenergizes to prepare a circuit for the rotary magnet 62.

Vhen the calling device at substation A is operated in accordance with the next and final digit of the called number, another series of interruptions is produced in the circuit of the line relay 51. This relay, in responding to these interruptions, causes the operation of the magnet 62'over the following 'test relay circuit: from ground by way 01 armature (53 and its back contact, armature 66 and its front contact, otl normal springs 67 and 68, armature 70 and its back contact, back contact and armature 75, armature v82 and its back contact and through the winding of the rotary magnet 62 to battery. Magnet 62 operates to rotate the wipers 0598, inclusive, of the switch into engagement with the bank contact set in connector l l associated with the line of the substation A, which, we will assume, are the bank contacts 123426, inclusive. The slow acting relay 56 energised in multiple with the rotary magnet and operates at its armature 77 to connect the test wiper 96 to the winding or the test relay 55, and at arn'iature 78 to short circuit the cont. ct springs comprising armature '4'5 and its back contact on the so as to guard against premature opening of the rotary magnet circuit in case the test relay 55 should be energized by the switch wipers, during their rotation, engaging bank contact sets associated with busy telephone lines.

Assuming that the desired line is busy at the present time, there will be a ground potential connected to the test contact 124, and the test relay 55 will be energized. Upon operating, relay 55, at its armature 74 clos a point in its locking circuit, which completed upon the deenergization of the slow acting relay 56, at its ar ature 75 opens the rotary magnet circuit and at its armature 76 connects a lead from the busy signalling machine to the lower heavy talking conductor. By the latter operation, the callingsubscriber is given an audible signal to inform him that the desired line is inaccessible at the present time. The release of the connection follows the replacement oi the receiver at the calling substation A. A detailed description of this release will be given hereinafter.

It will now be assumed that the line of the substation A is idle when the switch wipers of the connector H are brought into engagementwith the bank contacts 123-12b, lllCl'l'iSlVQ. 'Uuder these conditions, there will be no ground connected to the test con tact 124,- and the test relay 55 will not be energized. Then, upon the deenergization ot' the slow acting relay 56, a circuit is completed, which extends from ground by way ot front contact and armature 65, armature 7 1 and its back contact, through the upper winding of the marginally adjusted relay 58. through the upper winding of the switching relay 57, back contact and armature 77, test wiper 96, bank contact 12%, through the winding of the switching relay 150 in multiple with the resistance 151, and through the winding of the motor magnet 153 to battery. The relays 57, 5.8 and 150 are energized over this circuit, The relay 150, uponoperating, only partially attracts its armatures due to the mechanical interlocking device controlled by the armature of the line relay 152 but the armature is attracted enough, however, to disconnect the line of the called substation from its normal battery and ground connections in the line switch C. In the connector H, the relay 57 upon operating, establishes a locking circuit for itself at its armaturetll, at armature 82 opens the rotary magnet circuitand at armatures 70 and 83 completes'the signalling circuit. Another result of the energization of relay 5'7, is that at the armature direct ground is connected to the test contact 124 in order to busy the called line. Ringing current from the generator Gen is now intermittently projected out on the line of the substation A. 'lhernarginally adjusted relay 58 is ordinarily. not energized in series with the switching relay 5'? and the switching relay in the called line switch. However, on all lines; that are entitled to the special code calling service before mentioned, a re' sistance is connected in parallel with the switching relay in the called line switch. This may be seen in the line switch C, the resistance 151 being connected in parallel with the winding of the switching relay '150. Due to the resistance 151 being con-.

nected in multiple with the switching relay T 150, which permits a greater current flow, the relay 58 in the connector His energized. Upon operating relay 58 completes its own locking circuit at ari'nature 87, at armature 86 prepares a circuit for relay 59, and at armature 8d closes a circuit for the relay 105. Other results of the energization of relay 58 are. that at armature 88 ground is placed upon the vertical test contact 128 by way of the wiper 99, a circuit is prepared for relay 200 of the finder D at armature 89, and at armature 4:5 a signalling circuit is prepared. Relay 105, upon operating, at its armature 106 closes a circuit for the winding of the solenoid 107. The solenoid 10'? operates the plunger 110. Due to the dashpot 111, the plunger 110 takes a. considerable interval. of time before it operates the spring 108 into engagei'nent with its working contact.

It will first be assumed that the called subscriber at substation A responds before the spring 108 engages its working contact. Under these conditions,'the removal of the receiver at substation A. completes a circuit for the ring cut oil relay 54. Upon operating, relay 5%, establishes a locking circuit for itself at armature '72, at armatures 7'1 and 73 disconnects the ringing ourrent and at the front contacts of these arma tures finally completes the talking connection. Additional results of the energization is that at ,arinatures 418 and 47 the circuit of. the relay is opened and ground is removed from the vertical bankcontact 128 and from the test contact 125. The back bridge relay 50 supplies talking current to the substation A, while relay 51 supplies talking current to the substation A.

When the conversation is terminated, the calling and called subscribers will replace their receivers .upon their respective switchhooks. then the receiver is replaced at substation A, the line relay 51 deenergizes and opens the circuit of the slow acting relay 52. The latter relay deenergizes to open the locking circuit of relays 54, 5'7 and 58 in the connector H and also to complete the circuit of the release magnet 61. An

additional result of this deenergization is.

that the holding circuit of the switching relay 14 in the line switch C is opened. The release magnet 61 of the connector H operates to restore this switch. to normal, its own circuit being opened at the off normal springs when the switch shaft reaches its released position. the line switch C, deenergizes to restore the circuits of this switch to normal. In the above mannerthe connection is released.

It will now be assumed that the subscriber at substation A is in some other part of the building and consequently does not answer. In this case, when the spring 108 on the solenoid engages its working contact, a circuit is completed, which extends from ground by way of working contact of spring 108 and the said spring, through the primary winding of the induction coil 1, front contact and armature 89, conductor 160, through the winding of the start relay 200 in the finder D to battery' Relay 200, upon energizing, at its armature 210 prepares a circuit for relay 203 and at its armature 212 completes a circuit for the vertical magnet 205 of the finder D in multiple with the vertical magnet 310 of the code selecting switch F. Magnet 205, upon energizing, raises the switch wipers 240-243, inclusive, one step opposite the first level of bank contacts and at its armature 220 breaks its own circuit and the circuit of the vertical magnet 310 of the code selecting switch. Magnet 310 of the code selecting switch operates to raise the wipers 335 and 336 opposite the first level of bank cont acts. Another result of the upward anovement of the switch shaft is that the off normal springs are shifted, spring 213 placing ground on conductor 169 and disconnecting relay 203. The grounding of conductor 169 busies the code calling number and closes the circuit of relay 304 in the code selecting switch F. Relay 304 opens the release magnet current at armature 327. As the line of the substation A is not located in the first level of bank contacts the vertical test contact of this level will not be grounded and the ver- The switching relay 14, in

tical movements of the finder D and-the jcode selecting switch F will continue until is completed for the vertical test relay 201.

Upon operating, relay 201 establishes a locking circuit for itself at armature 218, at armature 219 opens the circuit of the vertical magnets 205 and 310 thereby stopping the vertical operation of the switches D and F and at the front contact of this armature transfers the operatingcircuit to the rotary magnets 206 and 309 of the finder andcode selecting switch, respectively. The rotary magnet 206 operates to rotate the wipers 240-242, inclusive, one step into engagement with the first set of bank contacts in the selected level and at its armature 225 opens its own circuit as well asthe circuit of the rotary magnet 309 in the code selecting switch F. Magnet 309 operates to rotate the wipers 335 and 336 into engagement with the first set of bank contacts in the first level. The intermittent operation of magnets 206 and 309 continues until the wipers 240-242, inclusive, arebrought into engagement with the set of bank contacts associated with the substation A in the finder D, which, it will be assumed, are the bank contacts 258260, inclusive. The slow acting relay 302 is energized in series with the rotary magnet 309 and maintains its armalVhen the finder wipers are brought into engagement with the above mentioned set of bank contacts, a circuit is completed which extends from ground by way of back contact and armature 47, front contact and armature 86 in the connector H, through the lower winding of the relay 59, wiper 97, bank contact 125, conductor 165, bank contact 259, wiper 241, and through the winding of the relay 202 to battery. Relays 59 and 202 are energized over this circuit. Relay 59, upon operating, establishes a locking circuit for itself at armature 91, completes the circuit of the upper winding ofthe ring out off relay 54 at armature 85, closes another circuit for the relay 105 at armature 93, and at armature 92 opens the circuit of the secondary winding of the induction coil 1. As the circuit of the relay 54 is completed by the energization of relay 59, the ring cut o'li' relay energizes. Upon operatin relay 5-: completes its own loclring one rent from the substation A, and prepares the talking connection. The operation of armature 43 is without function at the present time due to the fact that the relay 59 has completed another circuit for relay 105.

in the tinder D relay 202 operates to establish a locking circuit for itself at armature and it opens the circuits of the magnets .200 and 309 in the finder switch 1) and the code selecting switch F, respectively, at armature 2524i. Other results of the energization of the relay 202 are that at armature 222 a lead from the busy signalling machine is connected to the starting conductor 100 and at arn'iatures 221 and 223 the talking circuit is prepared. I

The wipers 335 and 330 of the code selecting switch F are now in engagement with the set of banlr contacts on the level which corresponds to the number of steps that the tinder D has taken in finding the line ot the substation A. This is the same as the number of the line of the substation A as the banks of the finder D are multipled with those of the local. connector switches. Thus the cone call number of each called subscriber corresponds to his directory niunber. By this arrangement, as the code selectingswitch F steps .in synchronism with finder D, the number of steps the finder takes in locating the line of the called party. selects the code. The arrangement of having banks of the finder D multipled with the corresponding contacts of the local connector switches is arbitrary. in tact, in larger private automatic exchange systems, in the majority of cases, it would be possible to bring all these special subscribers lines into the banks of an-ordinary one hundred line finder switch due to the fact that even in the larger private au tomaticexchange systems it is very seldom that there would be more than one hundred subscribers entitled to this special code calling service. T ms the selecting operation of the tinder D could still be utilized even in the large s stems to control the operation of the code selecting switch and selecting the code to be sent out.

it will be remembered that the slow acting relay 302 is energized in series with the rotary magnet 309. Upon operating, relay 302, at its armature 319 completes a circuit for the relay 303. The latter relay, upon operating, establishes a locking circuit for itself at armature 321 and at armature 320 prepares a circuit for the slow acting relay 305. At the termination of the rotary movement of the code selecting switch F, the slow acting relay 302 deenergizes and completes a circuit extending from ground by way of the armature .319and its back cont. disconnects the signalling cur-- tact, front contact and armature 320, armature 366 and its back contact, armature 331 and its back contact, and through the winding of the slow acting relay 305 to battery. Relay 305 operates at its armature 328 to complete a. circuittor the rotary magnet of the interrupter switch I. Magnet 365 operates to open the circuit of the slow acting relay 305 at armature 366. After a short interval the slow acting relay 305 deenergizes to open the circuit of the magnet 365. Magnet 365 deenergizesand advances the wipers 360and 361 of the code interrupter switchinto en 'a ement'with the bank contac'ts 369 and 370. The operation of the wiper 36lcompletes another circuit for the relay 303 so as'to prevent premature ending of the code in case the called subscriber should answer before a code is completed. This arrangement prevents a false signal being given. The operation of the wiper 360 places ground upon the conductor 370 extending to the next to uppermostleveloi bank contacts in the code selecting switch. However, as thewipersot'the switch are on the bank contacts 375 and 385 this operation 1219110 function at the present time. The magnet 365, up0n deenergizing, also again closes the circuit of the slow acting relay 305.

'Relay 305 operates to again close the rotary magnet circuit. The operation of the relay 305 and the magnet 365 continues until the wiper 360 of the interrupter switch I is rotated into engagement with the bank contact 372. When this occurs a circuit is completed extendingtrom grounded conductor 373 by way'ofwiper 360, bank contact 372, conductor 37 i, bank contact 375, wiper 335, through the winding of the relay 308and the r sistance 377 to battery. Relay 303 is energized over this circuit and, upon operating, establishes a locking circuit for itself at armature Other results of the energization of relay 308 are that at armature 332 a circuit is prepared for the differential relay 307 and at armature 331 the circuit of the slow acting relay 305 is opened and circuit closed at the front contact of this armature tor the slow acting relay 306. Relay 306, upon energizing, at its ari'natnre 329 closes another circuit for the slow acting relay 305. The latterrelay, upon energizing, at its armature 328 completes a circuit of the rotary magnet 365 of the codeinte rupter switch I. Magnet 365 energizes to open the circuit of the slow acting relay 306 at armature 366 and to close a circuit for the lower winding otthe differential wound relay 307 in multiple with the bells 338 and 339. The bells such as 338' and330 are located at various points in the establishment and serve to signal the called subscriber it he isany where in the building. The relay 307 operates at its armature 330 to close a circuit for its upperwinding. As the relay net 365.

307 is difierential, upon its energization the upper winding is energized and the armature 330 is retracted whereupon the relay again operates through its lower winding. This buzzer like actionof the armature 330 of the relay 307 serves to give a tone to the calling subscriber over a circuit which extend as follows: from battery by way of front contact and armature 330, back contact and armature 316, condenser, conductor 178, front contact and armature 228, wiper 242, bank contact260, conductor 164, bank contact 126, frontcontact and armature 83, armature 73 and its front contact, condenser, over the line of the substation A and through the upper winding of the line relay 51 to ground. In thismanner the calling subscriber is given a distinctive signal in order to inform him that the code is being sent out. As the circuit of the slow acting relay 306 is broken by the operation of armature 366, this relaydeenergizes and opens the circuit of the slow acting relay 305. After a short interval, relay 305 deenergizes and opens the circuit of the rotary magnet 365, which deenergizes also. The deenergization of magnet 365 advances the wipers 360 and 361 in the engagement with the next set of bank contacts and also closes a circuit for the slow acting relay 306. Upon the wiper 360 engaging bank contact 380 the relay 308 is short circuited and consequently deenergizes. Relay 308, upon retracting its armature, opens the circuit of the bells 338 and 339 and also of the relay 307 at armature 332 and at armature 331 it opens the circuit of the slow acting relay 306 and closes a circuit for relay 305. Relay 305 again operates to energize the rotary mag- The magnet. 365 energizes and opens the circuit of the slow acting relay 305 and operation of the relay 305 and the mag net 365 cause the wipers 360 and 361 to be rotated into engagement with the next set of bank contacts. l/Vhen the wiper 360 engages bank contact 382, a circuit is completed for the relay 308. The operation of relay 308 has the same functions as before,

.that is, its locking circuit is completed and also a circuit for the bells 338 and 339 and the interrupter relay 307 and also for the slow acting relay 306 isclosed. The magnet 365of the code interrupter switch I continues to advance the wipers 360 and 361 under the control of. the slow acting relays 306 and 305. It will be seen that at each deenergization of the magnet 365 the circuit of the relay 307 as well as the bells such as 338 and 339 is opened, thus a series of short rings are sent out. Vhen the wiper 360 engages bank contact 383, a circuit is completed which extends from grounded conductor 373 by way of wiper 360, bank contact 383, bank contact 385, wiper 336, and through the resistance 377 to battery. By

this operation the relay 308 is short circuited. The deenergization of relay 308 opens the bell circuit and also allows'magnet 365 to be operated under control of the single interrupter relay 305. The rotation of the wipers 360 and 361 continues and when the wiper 360 engages bank contact 372 the code ring is again started. It will be seen that during the ringing periods the magnet 365 of the code interrupter switch I is controlled by two slow acting relays 306 and 305, consequently this operation is slower than when it is controlled by the single slow acting relay 305. This latter condition occurs during silent periods.

The called subscriber upon hearing this code'ring will dial a special number, which is termed the code answering number, in order to converse with the calling subscriber. The operation when the called subscriber answers will be described with reference to the connector H, Fig. 1. It will be assumed that the connector H is operated into engagement with the bank contacts 115118, inclusive, which are the bank contacts associated with-the code answering number in the connector H. WVhen the engagement is made with this set of bank contacts the switching relay 57 is energized over a circuit extending from ground by way of front contactand armature 65, armature 74 and its back contact, through the upper winding of relay 58, through the upper winding of the switching relay 57, back contact and armature 77, test wiper 96, test contact 116, conductor 17 3 and through the winding of relay 300 to battery. The relays 57 and 300 are energized over this circuit. The operation of the relay 57 has the same result as before described among which is the com pletion of the ringing circuit. However,

immediately upon the energization of relay 57 a circuit is completed for the ring out off relay 54, which extends from battery through the upper winding of relay 54, back contact and armature 71, armature 79 and its front contact, wiper 95, bank contact 115, conductor 174, conductor 175, front contact and armature 221, wiper 240, bank contact 258, conductor 166, wiper of the connector used to extend the connection to the line of the subscriber called via armature and front contacts of armatures such as, 7 9 and 71 of the connector H, winding of the back bridge relay, such as 50 of the connector H, armature and front contact, such as 72, and the armature and front contact, such as 64, to ground. The relay 54 is immediately energized and operates to disconnect the signalling current and to complete the talking circuit. The relay 300 in the code selecting switch F, upon operating, opens one point in the circuit of relay 304 at armature 315, at the front contact of this armature places ground on conductor 169 to busy the code their respective switchhooks.

the ringing induction circuit. If the Wipers ot' the code interrupter switch are now nor-e mal the relays 3041-. and 303 deenergizes and the switch F will be released and the code stopped. it the code interrupter switchl is oil normal the relays 303 and 30 will be maintained energized until the wiper 361 comes to its normal position whereuponthe code selecting switch will be released as before; This arrangement prevents mutila tion of the code by its being stopped before being completed.

Conversation may now take place between the calling and called subscriber over the heavy talking conductors, battery being supplied to the calling subscriber "from the windings of the line relay'fil of the first calling connector H and to the called subscriber from the windings of the line relay of the connector used in extending the connection to the code answering number.

hen the conversation is terminated both subscribers will replace their receivers upon The replacement of the receiver at the called station brings about the release of the line switch and connector used in extending the connection to the code answering number in the usual manner. The release of the connector H and line switch G occurs responsive to the replacement of the receiver at substation A. Immediately upon the release otthe connector H the relay 200 in the finder D retracts its armatures and brings about the release of the finder. in the above manner the connection is release-d.

Should the subscriber called have not answered the release of the connections takes place in substantially the same manner as has already been described responsive to the replacement of the receiver at substation A, the diilerence in this casebeing that the code is stopped and the code equipment released by ground being removed from the conductor 18!) by the dcenergization oi relay 200. In this case also the release does not occur until the interrupter switch I is in its normal position.

It will be remembered that, when the finder switch D found the line of the substation A, at the energization of the relay 202, a lead from the busy signalling machine is connected to the starting conductor 160. This provision is made so that if some other subscriber should connect with one of these special service subscribers numbers he will receive a busy signal, inasmuch as the finder D cannot be operated to seize the line called. In order to explain this operation it will be assumed that the finder D was already in use when the subscriberat substation A extends a connection to the substation A. In this case the energization of the relay 58 bridges the secondary of the inductioncoil across the talking conductors in the connector H as the relay 59 is not energized. In this manner the calling subscriber is given the busy signal in order to inform him that he cannot communicate with the called subscriber, the tone being induced from the primary o-fthe induction coil in the starting circuit. occurs in the ordinary manner.

The above is the ordinaryoperation oithe system in handling these special service calls. Sometime in systems of this character situations are encountered wherein a certain party may have no definite locationan'd it is still desirable to be able to reach him at any time. In this case it will be seen that it is impracticable to give such party a telephone. However, in order to reach him or any other parties in like positions, what is known as a code calling number is provided. To call one of these parties itis only necessary to call this code calling number and then to dial the digits of the desired partys code. The code signal isthen sent out in the usual manner.

The above operation will now be briefly described. For this purpose it-will be assumed that the subscriber at substation A desires to call one of these special parties. To accomplish this result, the subscriber at the calling substation will remove, his receiver and operate his calling device for the two digits of the code calling number. It will be assumed that these operations cause the calling line to be extended by way of the line switch C to the connector H and that this connector is in turn operated until its wipers are brought into engagement with The release of this connection the bank contacts 119-122, inclusive, which are the bank contacts associated with the code calling number in the connector. H. When this occurs, assuming that the cope calling number is idle, the switching relay 5'? is energized in series with the relay 304 in the code selecting switch F. The operations of the relay 5! are the same as before stated with the exception that ringing current is not projecteo out over the wipers 95 and 98. The reason that ringingcurrent is not projected out on these wipers is that, when the wipers of the connector are rotated into engagement withthe code calling set of bank contacts, the camspring 90 which is operated only on code numbers, is operated to disconnect the ringing current and to prepare a dialing circuit. The operation of this spring is controll d by a cam on a switch shaft in a well known manner.

The calling subscriber will now operate his calling device for the first digit in the code number of the desired partyQfBy this opration of the line relay its armature 63 is caused to vibrate a plurality of'times corresponding in number to thenumber of interruptions in the digit dialed. At each retraction of the armature 63, an impulse of current is sent over a circuit extending from ground byway of armature 63 and its back contact, armature 66 and its front contact, off normal springs 67 and 68, armature 70 and its back contact, back contact and armature 75, armature 82 and its front contact, working contact of spring 90 and the said spring, back contact and armature 73, armature 83 and its front contact, wiper 93, bank contact 122, conductor 167, conductor 174, off normal springs 323 and 32 1, through the winding of the slow acting relay 301 and through the winding of the vertical magnet 310 to battery. The above is the circuit over which the first impulse is sent to the vertical magnet. However, upon the first operation of the vertical magnet, the off normal springs are shifted and the remaining vertical magnet impulses are sent over another circuit, which is similar to the one above traced, except that it goes through off normal springs 323 and 325 and armature 317 on the slow acting relay 301, which is now energized. Magnet 310 operates to raise the wipers 335 and 336 step by step until these wipers are placed opposite the desired level of bank contacts. Shortly after the end of the vertical motion of the switch, the slow acting relay 301 deenergizes and prepares a circuit for the rotary magnet 309.

When the calling device at the calling substation A is operated in accordance with the next and final digit in the desired number, the line relay 51 in the connector H again deenergizes a plurality of times. At each deenergization an impulse of current is sent to therotary magnet 309 of the code selecting switch F over a circuit similar to the one previously traced. Magnet 309 operates to rotate the wipers 335 and 336 into engagement with the proper set of bank contacts to send out the desired code. The slow actingrelay 302 is energized in series with the rotary magnet andoperates at its armature 319 to close a circuit for the relay 303 and at armature 318 to short circuit the contact springs comprising armature 322 and its back contact on the relay 303. The relay 303 immediately energizes and at its armature 322 opens one point in the circuit of the rotary magnet, at armature 321 establishes a locking circuit for itself and at armature 320 prepares a circuit for the slow I acting relay 305. The subsequent operations of the code interrupter switch I, and the code ringing takes place as hereinbefore described. The called subscriber answers by going to the nearest telephone, removing the receiver thereat, and operating the calling device for the two digits of the code answering number. The results which occur responsive to this operation take place in the of the local connector switches.

same manner as has already been fully described.

It will be remembered as soonias the finder D steps off normal ground is placed upon the conductor 169. This operation serves two functions the first of which is to energize the relay 304. in the code selecting switch F and the other to place a ground potential upon the test contact associated with the code calling number in the banks In this manner it is impossible to use the code calling number while the code selecting switch is in use for an ordinary call.

Should the code selecting switch bein use for one of these special calls when ground is placed upon the starting conductor 160 in the ordinary operation of the system, the energization of the relay 200 completes a circuit for the relay 203. Relay 203, upon operating, at its armature 229 opens the circuit of the vertical magnet of the finder, at armature 227 establishes a locking circuit for itself and at armature 226 connects a lead from the busy signalling machine to the start conduct-or 160. By the latter operation the calling subscriber is given an audible signal in order to inform him that the called subscriber is inaccessible. The release of the connection in this case occursin the usual manner responsive to the replacement ofthe receiver at substation A.

The features of the invention having been described and ascertained what is thought to be new and desired to have protected by Letters Patent will be pointed out in the appended claims. a

What I claim is:

1. In a telephone system, an automatic switch, telephone lines accessible thereto, code signalling. equipment, a. signalling circuit, means for operating said automatic switch toconnect with one of said lines, timing mechanism rendered operative responsive to connection with said line, and an automatic switch controlled by said timing mechanism for selecting a code and initiating the operation of said code signalling equipment to apply code signalling current to said circuit.

2. In a telephone system, an automatic switch, telephone lines accessible thereto, a source of ringing current, code signalling equipment, a signalling circuit, means for operating said automatic switch to connect with one of said lines, means operative responsive to the establishment of said connection for connecting said source to said line, timing mechanism rendered operative responsive to connection with said line, and means controlled by said timing mechanism for selecting a code and for connecting said code signalling equipment to said circuit.

3. In a telephone system, an automatic switch, telephonelines accessible thereto, a

" source of ringing current, code signalling equipment, a signalling circuit, means for operating said automatic switch to connect with one of said lines, means operative responsive'to the establislnnent of said connection for connecting said source to said line, timing mechanism rendered operative responsive to connection with said line, meanscontrolied by said timing mechanism for connecting said code signalling equipment to said circuit, a second automatic switch controlled from any other of said lines for connecting with said first calling line, and means operative responsive to the establishment of said last connection for disconnecting said code signalling equipment.

4. In a' telephone system, an automatic switch, telephone lines, code 7 signalling equipment, a signalling circuit, a finder switch, means for operating said automatic switch from a calling one of said lines to establish a connection with a called one or said lines, means operable a predetermined time interval atter said connection is established for operating saidfinder switch to connect with said line, a code selecting switch and means for operating it in synchronism with said finder to select a code and for then applying said code to said circuit.

5; In a telephone system, an automatic switch, telephone lines, code signalling equipment, a signalling "circuit, a finder switch, means for operating said automatic switch from a calling one of said lines toesta'bl-ish a connection with a called one or said lines, means operable a predetermined time interval after said connection is established for operating said finder switch to connect with said line, a code selecting switch and means for operating it in synchronism with said finder to select a code and for then applying said code to said circuit, and another automatic switch controlled from "another calling one of said lines for connecting with said first calling line whereby a telephonic connection is established between said caning line's.' I

6. In a telephone system, an automatic switch, telephone lines, code signalling equipment, a signalling circuit, a finder switch, means for operating said automatic switch from a calling one of said lines to establish a connection with a called one of said lines, means operable after a predetermined time interval after said connection is established for oper'atingsaid finder switch to connect with said line, a code selecting switch and means for operating it in synchronism with said finder to select a code and itor then applying'said code to said cir-- cuit, another automatic switch controlled from another calling one of said lines for connecting with said first calling line whereby a telephonic connection is established between said calling lines, and means operative when the last mentioned "connection is established for disconnecting said code signalling equipment from said circuit.

7. In a telephonesystem, a group of connee-tor switches, telephone lines, a (finder switch common to said group, a code select-I ing switch associated with said finder, a signalling circuit, means for operating any one or said connectors to connect with one of said "lines, means operative a predetermined time interval after said connection established for operating said finder to find said called line, and means for operating said code" selecting switch in synchronism with said finder to select a code ring.

*8. In a telephone system, groap'o'f connector switches, telephone lines, a finder switch common to said group, a code select: ing switch associated with "said finder, a signalling circuit, means for operating any one of said "connectors "to connect with one of said lines, means operative a predeten mined time interval after said connection is established for operatingsaid finder to said called line, means for operatingsaid code selecting switch in synchronism with said finder to select a code ring apply 7 it to-said circuit, 'andmeans for operating another of said connectors to connectfwi'th said first calling line and to] release said code selecting switch. a

9. In a telephone system iine, "automatic switches tor connecting with said line co'de ringing equipment, a code selectiiig switch common to said automatic switches, a finder switch associated with said 'codeselector switch, means "for operating said finderto connect said code selector switch with said line, and means for operating said c'ode selecting switch insynchroni'sm with said finder. i

10. In a telephone system, a line, means for seizing said line, code ringing equipmerit, a signalling circuit, a'code selecting switch, a finder switch associated therewith, means for operating said finder automatically in response to said seizure to connect with said line, means for operating said code selecting switch in synchronism with said finder, and means for thereafter applying the selected code to said circuit.

11. In a telephone system, a line, means for seizing said line, a finder switch, means for operating said finder in response to said seizure to connect with said line, and a code selecting switch controlled by said finder toselect a code ring.

1 2. In a telephone system, a group of connector switches, a. finder switch common thereto, telephone lines, means for operating anyone of said connectorswitches to connect with one-oi said lines, a code selector switch, means controlled by such connection for operating saidrfinderi switch to connect said'c'ode selector switch with said called a line, and for causing said code selecting switch to selecta code, a tone machine, means for.operating anotherof said connectorsto connect with another of said lines and means controlled by said finder for connecting a lead from said tone machine to said other connector. Z 1 13, In 'a telephone system, subscribers vlines, common. signalling mechanisms, means 'controlled from any line for seizing said mechanisms via one path and transmitting code signals, means for extending a connection from a calling to a called one of said ,lines, and means operatedif the calledsubscriber does not answer for automatically connecting said called line with said mechanisms via another path and transmitting a code signal thereover.v I i v 14.111 a. telephonesystem, subscribers lines, a set of signals common to said lines, mechanisms for operating said signals in accordance with vdifferent codes, means controlled from any line for seizing said mechanisms and operating them directively to select a code and for operating the signals in accordance therewith, and means for seizing the mechanisms through a switch associated with acalled one of said lines and causing them to automatically operate to select a certain code and operate the signals in accordance therewith.

, 15. In a telephone system, subscribers lines, a common signalling circuit, mechanisms associated with the circuit, means controlled from a line forseizing the mecha nisms and directively operating them to select a code and transmitsignals over the 4 circuit 1n. accordance therewith, means for extendinga connection to one line from 'another, and means responsive thereto for seizing said mechanisms and causing them to automaticallyselect a code corresponding to the called line and transmit signals over the circuit in accordance therewith.

16. In a telephone system, subscribers lines, automatic-switches any one of which may be used for interconnecting anytwo of said lines, a'signal individual to each of said lines, a signal common to said lines, means in the Switch used for causing the individualsignal of the desired lineto be actuated, means operative to disconnectsaid signal upon removal of the called subscribers receiver, means forautomatically disconnecting said signal after a definite period should the called subscriber fail to answer, means for causing the common signalto be then operated in the characteristic manner, and means under the control of a subscriber at the station of any of said linesfor seizing and operating an idle one of saidautomatic switchesto cause said comlines, a plurality of connector switches availcircuit completed. I

a 17. In a telephone system, called lines of two classes, a code selecting and signallingswitch, means for causing said switch to antomatically operate to select a particular code when a. line of one class is called, and means for directively operating said switch when a' line of theother class iscalled.v

18. In a telephone system, subscribers mon signal to be disconnected and a talking able for use inextending talking connections to or fromsaid lines, a signal common to said lines, means for operating one of said switches to extend a connection from a calling to a called one of said lines, means common to said connector switches causing saidcommon signal to operate in a character, istic manner dependent on the line connected with, means for seizing and operating one of said connector switches to extend a,connection to a calling line, and means responsive to the seizure of .the calling line for disconnecting said common signal,

19. In a telephone'system, a code called line, means for extendinga connection to said line, a code selector switch, a signalling device, means for directively operating said switch to select a code and forcausing said ignalling device to be operated in accordance therewith, a subscribers line, said first 95 means operable to extenda connection to said subscribers line and efi'ectiveto operate signal thereat, and .means effective, after a delayi'or causing said code selector switchto automatically operate to select'a code and to cause said first signal tooperate in accordance therewith.

20. In an automatic-telephone system, a plurality of subscribers lines, a plurality of automatic switches accessible to. said lines, banks for said switches, said banks being multipled so thatIany of said switches has access to any line in saidsystem, aafinder' switch providedgwith 'a bank, said bank be-t ing multipled to said other switch bank, a code switch and signalscontrolled thereby, means for operating one of said first switches to extend a connection from a calling to a called one of saidlines,- and-means controlled through saidengaged switch operative after a definite. intervalif the called party does not answer to cause said finder to automatically associate itself with said called line andto cause said code switch to operate said signals in a manner characteris. tic of said called line.- a 21. In a telephone system, lines, a con-- nector switch for completing connections between said lines, signalling equipment insaid switch for'signalling called lines, code: signalling equipment including line select ing and code selecting switches, means in cluding wipers on the connector switch, ef-

iective each time a connection is set up to a called line, for placing a test potential upon contacts of the bank of said line selecting switch which are individual to the line called, means effective after an interval providing the called subscriber fails to respond for causingthe lineselecting switch to hunt for and seize the called line, and

means for causing the code selecting switch to select a code contingent on the line se- 10 lected.

In Witness whereof, I hereunto subscribe my name this 1st day of November, A. D. 1922.

JOHN E. GARDNER.- 

